A : `NO_2+COoverset("Slow")rarrCO_2+NO`
Rate `=K[NO_2]^2`
R : Rate does not depend upon [CO] because it is involved in the first step.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion , then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion , then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements , then mark (4)

Answer

To solve the question, we need to analyze the assertion and reason provided, focusing on the reaction and the rate law.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
The given reaction is:
\[ \text{NO}_2 + \text{CO} \overset{\text{Slow}}{\rightarrow} \text{CO}_2 + \text{NO} \]
This indicates that the reaction proceeds in a slow step, which is crucial for determining the rate law.

2. **Identifying the Rate Law**:
The rate law is given as:
\[ \text{Rate} = k[\text{NO}_2]^2 \]
This suggests that the rate of the reaction depends on the concentration of \(\text{NO}_2\) squared, but does not include \([\text{CO}]\).

3. **Analyzing the Assertion**:
The assertion states that the rate of the reaction is given by the expression \(k[\text{NO}_2]^2\). Since this is the rate law provided, we can conclude that the assertion is true.

4. **Analyzing the Reason**:
The reason states that the rate does not depend on \([\text{CO}]\) because it is involved in the first step. However, the rate of a reaction is determined by the rate-determining step (RDS), which is the slowest step in the reaction mechanism. In this case, the slow step is the one that determines the rate, and the presence of \([\text{CO}]\) does not contribute to the rate law as shown.

5. **Conclusion**:
Since the assertion is true (the rate law is correctly stated), but the reason is false (the rate does not depend on \([\text{CO}]\) because it is not part of the rate-determining step), we conclude that:
- The assertion is true.
- The reason is false.

Thus, the correct answer is that the assertion is true, but the reason is false.

### Final Answer:
The correct option is 3: Assertion is true, but reason is false.